1. Field of the Invention
The present invention relates to a method of and an apparatus for controlling stacking of a load by a crane. More particularly, the present invention relates to the method of and the apparatus for controlling stacking of a load by a crane which is positioned a tool of the crane at a target position, is allowed to land, or in which load held by the tool is positioned at the target position and stacked.
2. Description of the Related Art
A typical example of the above-mentioned apparatus is a crane (i.e. a container transfer crane. Hereafter xe2x80x9ctransfer cranexe2x80x9d) which stacks containers one above the other. This transfer crane positions a tool or a load (i.e. the container) held by the tool at a desired target position, and then makes the tool or the load to land and thus stacks the tool or the load. The crane has a trolley (transverse trolley) which moves in the horizontal direction along a camber of a crane bodywork. The tool which supports the load is hung down from the transverse trolley using a rope. The tool ascends and descends when the rope is reeled or unreeled. The rope is reeled or unreeled using a reeling apparatus mounted on an appropriate position in the trolley or the crane itself.
When the tool or the load is to positioned on the target position and the tool or the load is landed or stacked, it is necessary to control such that horizontal deviation is not caused between the target position and the tool or the load at the time of stacking or landing. As a technique which controls this kind of landing, there is one shown in Japanese Patent Application Laid-open No. 10-120362.
In the landing control apparatus shown in Japanese Patent Application Laid-open No. 10-120362, amount of swing of the load in the horizontal direction is measured by a detector. Then, future horizontal position of the load is estimated and calculated based on assumption that horizontal motion of the load is in the form of a sine wave of a simple pendulum. The future horizontal position of the load is estimated using swinging speed of the load calculated by time variation in singing amount. If the calculated future position of the tool coincides with the target position, then descending speed of the tool is controlled in accordance with estimating timing, and control is carried out such that the load precisely reach the target position.
The landing control apparatus described in Japanese Patent Application Laid-open No. 10-120362 uses a simple pendulum having a fixed hanging point, as a model which estimates a future horizontal position of the load. In landing control described in Japanese Patent Application Laid-open No. 10-120362, the trolley is on a constant position while landing is controlled, and the control is unconcerned for position control of the load in the horizontal direction.
There is no problem with the technology described in Japanese Patent Application Laid-open No. 10-120362 using a simple pendulum model when the body of the crane is sufficiently rigid and it is judged that a rope hanging point on the trolley is substantially fixed. However, when the rigidity of the crane bodywork is low and a rope supporting point on the trolley can not be regarded as a fixing point and if the simple pendulum model is used to approximate a motion of the system of load and rope, then a large error is generated in a value of an estimated future load position. This causes an inadmissible deviation in real and future positions of the load. If the crane is a gantry crane having tall legs or a tire-running type crane, then the variation in the position of the trolley (xe2x80x9ctrolley positionxe2x80x9d) generated by deformation of leg structure or tire is large, and it can not be ignored.
In some of ropes which support the load, an auxiliary rope disposed is in an inclining manner is added to give a force in the horizontal direction to the load, thereby obtaining swing preventing effect. If a simple pendulum model is used, a large error may be generated in estimation of position of the load.
Furthermore, in the technology described in Japanese Patent Application Laid-open No. 10-120362, descending timing of the load is controlled such that the horizontal direction position of the load coincides with time point when permissible range is obtained with respect to a target position while a trolley position, i.e., a rope fulcrum position which supports the load is fixed. However, when a large deviation in horizontal direction exists between the trolley position and a position on the ground where the load is to be stacked, it is necessary to correct the position of the trolley also. However, even if the trolley position is corrected, new horizontal motion of the tool is generated, which affects estimation of future position of the tool and as a result, time required for controlling the landing control is increased in some cases.
It is an object of the present invention to provide a method of and an apparatus for controlling stacking of a load by a crane capable of allowing a load to land with high precision and capable of shortening time required for the landing operation even if the trolley position of the rope is varied due to deformation or swing, and even if a rope system can not be regarded as being simple pendulum. Moreover, this invention provides a method of and an apparatus for controlling stacking of a load by a crane capable of enhancing loading efficiency by reducing labor of a crane operator.
The method of controlling stacking of a load by a crane according to one aspect of the present invention is applied to a crane having a trolley which moves in a horizontal direction, a tool which is hung down using a rope from said trolley and which holds said load, and a rope reeling unit which reels or unreels said rope and thereby ascends or descends said load and stacks said load or said tool to a desired position. This method comprises estimating periodical displacement of said tool in a horizontal position, estimating a speed with which said tool descends in such a manner that said tool or said load lands on the desired position while an amplitude of the estimated periodical displacement becomes maximum, and controlling reeling or unreeling of said rope by said rope reeling unit in such a manner that said tool or said load descends at the estimated speed.
The method of controlling stacking of a load by a crane according to another aspect of the present invention is applied to a crane having a trolley which moves in a horizontal direction, a tool which is hung down using a rope from said trolley and which holds said load, and a rope reeling unit which reels or unreels said rope and thereby ascends or descends said load and stacks said load or said tool to a desired position. This method comprises estimating periodical displacement of said tool in a horizontal position, positioning and stopping said trolley at a trolley stop position which is deviated from a stacking target position by a distance corresponding to a maximum amplitude of the periodical displacement, and estimating a speed with which said tool descends in such a manner that said tool or said load lands on the desired position while an amplitude of the estimated periodical displacement becomes maximum, controlling reeling or unreeling of said rope by said rope reeling unit in such a manner that said tool or said load descends at the estimated speed.
The apparatus for controlling stacking of a load by a crane according to still another aspect of the present invention controls a crane having a trolley which moves in a horizontal direction, a tool which is hung down using a rope from said trolley and which holds said load, and a rope reeling unit which reels or unreels said rope and thereby ascends or descends said load and stacks said load or said tool to a desired position. This apparatus comprises an estimating/calculating unit which estimates or calculates periodical displacement of said tool in a horizontal position, a speed estimating unit which estimates a speed with which said tool descends in such a manner that said tool or said load lands on the desired position while an amplitude of the estimated periodical displacement becomes maximum, and a rope reeling control unit which controls reeling or unreeling of said rope by said rope reeling unit in such a manner that said tool or said load descends at the speed estimated by said speed estimating unit.
The apparatus for controlling stacking of a load by a crane according to still another aspect of the present invention controls a crane having a trolley which moves in a horizontal direction, a tool which is hung down using a rope from said trolley and which holds said load, and a rope reeling unit which reels or unreels said rope and thereby ascends or descends said load and stacks said load or said tool to a desired position. This apparatus comprises an estimating/calculating unit which estimates or calculates periodical displacement of said tool in a horizontal position, a trolley stopping unit which positions and stops said trolley at a trolley stop position which is deviated from a stacking target position by a distance corresponding to a maximum amplitude of the periodical displacement, a speed estimating unit which estimates a speed with which said tool descends in such a manner that said tool or said load lands on the desired position while an amplitude of the estimated periodical displacement becomes maximum, and a rope reeling control unit which controls reeling or unreeling of said rope by said rope reeling unit in such a manner that said tool or said load descends at the speed estimated by said speed estimating unit.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.